Propane treating of top crude to produce asphalt and gas oil



March 28, 1967 PROPANE TREAT I NG J. VAN POOL Filed Sept. 11, 1964 GAS OIL (PROPANE EL wAx) Q sTEAM S GAS on.

(PROPANE &HEAVY wAx) TOPPED CRUDE 2 56 2? 2 6" '7 22 2 STEAM PROPANE 24 -ASPHALT RESIDUE I is 32 3 4 (I I M- 38 g i so E; STEAM STEAM 36 INVENTOR.

JOE VAN POO L ATTORNEYS United States Patent 3,311,551 PROPANE TREATHNG OF TOP CRUDE TO PRO- DUCE ASPHALT AND GAS 011.

Joe Van Pool, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Sept. 11, 1964, Ser. No. 395,867 7 Claims. {CL 208-45) This invention relates to a process and apparatus for the two-stage treatment of topped crude oil to produce a substantially wax-free asphalt and gas oil.

The propane extraction or treatment of topped crude to produce an asphalt of low wax content is conventional in the petroleum industry. Crude oil is generally subjected to atmospheric distillation to recover separate streams of light gases, gasoline, kerosene, and gas oil, leaving a bottoms stream of residual material amounting to about 40 percent by volume of the original crude oil. This residual stream is then subjected to vacuum distillation to further reduce the residuum to the range of about to percent by volume of the original crude oil and recover additional quantities of gas oil. The vacuum reduced crude or residuum is then propane treated or extracted to reduce the wax content of the residuum and produce an asphalt of low wax content which is suitable as an asphalt cement for road construction and similar application.

It has been found that the treatment of some crude oils in accordance with the foregoing process results in the production of an asphalt of too high a wax concentration to permit use thereof as road building material. One such crude oil is the Rangely crude from the western Colorado area. This crude oil has been successfully treated by subjecting the crude oil before atmospheric and vacuum distillation to a centrifuging step to recover a substantial proportion of the wax content. This centrifuging step is expensive in that it requires rather expensive equipment and is time consuming.

This invention is concerned with -a process and apparatus for treating a topped crude oil of high wax content which produces an asphalt substantially free of Wax.

Accordingly, it is an object of the invention to provide a process and arrangement of apparatus for the propane treatment or extraction of a topped crude oil which produces a substantially wax-free asphalt. Another object is to provide a process and apparatus for the propane treatment of a topped crude of high wax content which eliminates the need of centrifuging the original crude oil prior to the topping procedure. A further object is to provide a process and apparatus which produces a substantially wax-free asphalt from a topped crude of high wax content in a more economical manner than heretofore available. It is also an object of the invention to provide a process and apparatus for the propane treatment of a topped crude of high wax content which produces a substantially wax-free asphalt and also a second gas oil stream of exceptionally low metal content. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises subjecting a topped crude of relatively high wax content to propane extraction in two separate columns in series and operating the second column at a substantially higher temperature than the first column, thereby producing an asphalt substantially free of wax. The propane treatment step in the first column or tower is substantially the conventional treatment of the topped crude effected in the prior art in a single column. The treatment in the second tower or column is effected at temperatures at least 20 F. above the average temperature in the first column. To illustrate, the temperature in the lower section of the first column is maintained in the range of 100 to 160 F. and preferably in the range of 115 to 130 F. while the tempera- 3 ,311,551 Patented Mar. 28, 1967 ture in the upper section of the first column is maintained in the range of to 180 F. and preferably to F. The temperature in the lower section of the second column is maintained in the range of 150 to 190 F. and preferably in the range of to 185 F. while the temperature in the upper section of the second column is maintained in the range of to 200 F. and preferably in the range of to F. The temperature in the upper section of each column is maintained substantially above the temperature of the lower section. Sufficient pressures are maintained in the two columns to assure liquid phase operation. The pressure in the first column is generally maintained in the range of 500 to 700 p.s.i.g. and the pressure in the second column is generally maintained in the range of 400 to 600 p.s.i.g.

The volume ratio of propane to topped crude in the first column is controlled in the range of 3 to 10 while the volume ratio of propane to asphalt feed to the second column is maintained in the range of 1 to 4.

A more complete understanding of the invention may be had by reference to the accompanying drawing which is a schematic flow illustrating a preferred arrangement of apparatus for effecting the invention. A first propane treating column 10 is provided with a topped crude feed inlet line 12 entering an intermediate section of the column, a propane feed inlet line 14 entering the bottom section of the column, an effluent gas oil line 16 communicating with the top of the column, and an efiluent asphalt line 18 leading from the bottom of the column. Heating means in the upper section of the column comprising a steam coil 20 supplies heat to the column as required to maintain a suitable temperature differential between the bottom and top sections of the column. A level controller 22 in the lower section of the column senses a liquid or interface level between the gas oil phase and the asphalt phase and controls the withdrawal rate of asphalt thru line 18 by regulating valve 24. In some instances it is desirable to feed a portion of the propane from line 14 into the topped crude oil in line 12 and line 26 having a control valve therein is provided for this purpose. A second propane treating column 30 has an intermediate feed inlet connected by means of line 32 with line 13 for-feeding the propane-asphalt mixture removed as a bottoms stream from column 10. An indirect heat exchanger 34 in line 32 serves as a heating means for the feed passing thru line 32 when temperature control in column 30 is effected in part by heating this stream. A lower inlet in column 30 connects with line 36 which leads from propane line 14. A heat exchanger 38 in line 36 provides for temperature control of the propane stream as a means of controlling the temperature in column 30. Line 40 is an alternative line for injecting propane directly into line 32 to provide the desired ratio of propane to asphalt in the feed to column 30. All or part of the propane required to provide the desired ratio may be passed thru line 40. Steam coil 56 provides heating the top of column 30.

Efliuent line 42 connects with the top of tower 30 and serves as a gas oil withdrawal line. Any part or all of the gas oil may be passed thru line 44 into line 16 to mix with the gas oil from column 10. It is desirable in some instances to separately recover the gas oil from line 32 and this is accomplished by opening the valve in line 46 and closing the valve in line 44. The extremely low metal content of the gas oil in lines 42 and 46 makes it desirable to separately treat this stream as by hydrocracking to produce gasoline and distillate in a so-called clean oil unit, whereas the gas oil in line 16, containing a higher metal content is treated in a so-called dirty oil unit.

A level controller 50 senses an interface level in the lower section of column 30 and controls motor valve 52 in asphalt withdrawal line 54 to maintain a selected level of asphalt in this column similarly to the action of liquid level controller on column 10. When desired an indirect heat exchanger such as a steam coil 56 is provided in the upper section of column 30 as a means of maintaining adequate temperature differential between the top and bottom sections of this column. This heat exchanger may be used to supplement the heat supplied to the column by heaters 34 and/or 38.

To illustrate the invention, a crude oil comprising 35 volume percent Red Wash crude and 65 volume percent Rangely crude was topped in conventional manner by atmospheric distillation to produce the usual cuts and the residual crude oil from the bottom of the distillation column amounted to 48.0 volume percent of the original crude. This residual crude oil was subjected to vacuum distillation to provide further conventional cuts and aresidual bottoms stream which amounted to 39.5 volume percent of the original crude. The wax concentration was 3.0 Wt. percent in the original mixed crude and 7.1 wt. percent in the feed to the first propane column. The residue from the vacuum distillation unit was propane extracted in successive columns substantially as described herein. The results of the run are presented in the table below:

TABLE Column 1 2 Top Temp, F 140 189 Bottom Temp, F 122 180 P.s.i.g 600 475 Solv./Oil Vol. Ratio 4.9 3.0 Asphalt Product:

Residue (Vol. Percent of Crude Oil) 5.1 4. Wax Content. Weight Percent 9.8 2.0 Ring and Ball S.P., F 219 190 Oliensis Spot Test Gas Oil Product:

Vanadium (as V), p.p.n1 1 1 Nickel (as Ni), p.p.m 13.6 3. 7 Bamshottom C.R., Weight lercentn 3.8 1. 23 Apparent Wax 5 (Thin Film Test) 1 Positive. 2 Negative. In asphalt. 4 Thin coat of waxy material. 5 None. (Possible trace.)

The foregoing data illustrate the fact that a topped crude oil containing a high percentage of heavy wax can be propane treated in accordance with the invention so as to produce a substantially wax-free asphalt without preliminary centrifuging of the original crude. The data also demonstrate the relatively low metals content, particularly, with respect to the nickel which renders the gas oil product stream from the second column readily amenable to separate hydrocracking in a clean oil unit separately from the gas oil recovered from the first propane extraction column which is substantially higher in nickel content. The nickel and other metals such as vanadium have a strong influence on the hydrocracking operation and produce considerably more coke than normally results from hydrocracking a feed free of these metals.

It is to be understood that the dew-axed asphalt stream from column 30 is passed thru line 54 to further processing steps to remove residual propane by such methods as flashing and stripping with steam to provide an asphalt cement base substantially free of wax and marketable as such.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A process for producing asphalt and gas oil from a topped crude oil of high wax content without centrifuging to remove wax which comprises the steps of:

(a) treating said topped crude oil in a first propane deasphalting zone with about 3 to 10 volumes of pro- 4 pane per volume of crude oil at a temperature in the range of about to 180 F.;

(b) recovering an overhead stream from the first zone of step (a) comprising propane and gas oil;

(0) recovering a bottoms stream from the first zone of step (a) comprising asphalt and propane;

(d) adjusting the propane-asphalt ratio of the bottoms stream of step (c) to the range of 1:1 to 4:1 and passing the resulting stream to a second propane deasphalting zone maintained at a temperature in the range of about 150 to 200 F. and at least 20 F. above the average treating temperature in the first zone of (a) to produce an asphalt bottoms stream substantially free of wax and an overhead stream of propane and gas oil of improved gas oil quality; and

(e) separately recovering the bottoms stream and the overhead stream of step (d).

2. A process for producing a substantially wax-free asphalt and a gas oil from a topped crude oil stream of high wax content which comprises the steps of:

(a) treating said topped crude oil stream (without centrifuging to remove Wax) in admixture with propane at a volume ratio of propane to crude oil in the range of 3 to 10 in a first upright propane deasphalting zone operated at a bottom temperature in the range of 100 to 160 F. and a higher top temperature in the range of 130 to 180 F. and in liquid phase;

(b) recovering from the first zone of step (a) an overhead gas oil-propane stream and a bottoms asphaltpropane stream containing wax; and

(c) adjusting the propane-asphalt volume ratio of the asphalt-propane stream of step (b) to the range of 1:1 to 4:1 and substantially lower than in step (a) and treating the resulting stream in a second upright deasphalting zone at higher average temperatures (at least 20 F.) than in step (at) including a bottom temperature in the range of 150 to 190 F. and a higher top temperature in the range of 180 to 200 F. and in liquid phase, so as to produce a bottoms stream of asphalt substantially free of Wax and an overhead stream of propane-gas oil containing wax.

3. The process of claim 2 further comprising maintaining in the first zone of step (a) a bottom temperature in the range of to F., a top temperature in the range of to F., and a pressure in the range of 500 to 700 p.s.i.g., and maintaining in the second zone of step (c) a bottom temperature in the range of to F. and higher than the bottom temperature, a top temperature in the range of 185 to F., and a pressure in the range of 400 to 600 p.s.i.g.

4. The process of claim 2 wherein the higher temperature in the second zone of step (c) is maintained by passing a stream of propane to said second zone, heating said stream of propane, and control-ling the temperature thereof to provide said higher temperature.

5. Apparatus comprising in combination:

(a) a first propane deasphalting column having inlet means for topped crude and for propane in an intermediate section, outlet means for a propane-gas oil stream in the upper end, outlet means in the lower end for propane-asphalt, indirect heating means in the upper end, and means for maintaining an interface level between an asphalt phase and a gas oil phase in a lower section thereof;

(b) a separate second propane deasphalting column having inlet means for a propane-asphalt stream connected directly by conduit means with the outlet means of (a) for propane-asphalt, outlet means for a propane-gas oil stream in the upper end, outlet means for a dewaxed product asphalt stream in the lower end, and means for maintaining an interface level between an asphalt phase and a gas oil phase in a lower section thereof; and

(0) means for maintaining a higher temperature in the second column of (b) than in the first column of (a).

5 6. The apparatus of claim 5 wherein the means of (c) comprises a heat exchanger in the conduit means of (b). 7. The apparatus of claim 5 including a separate line for propane leading into the second column of (b) and indirect heating means in said separate line.

References Cited by the Examiner UNITED STATES PATENTS 2,205,613 6/1940 Bahlke et a1. 208-309 6 Dickinson et a1. 208-45 Dickinson et al 208-45 Benedict et a1 208-309 Ill'man 208-45 Garwin 208-45 P. KONOPKA, Assistant Examiner.

DANIEL E. WYMAN, Primary Examiner. 

1. A PROCESS FOR PRODUCING ASPHALT AND GAS OIL FROM A TOPPED CRUDE OIL OF HIGH WAX CONTENT WITHOUT CENTRIFUGING TO REMOVE WAX WHICH COMPRISES THE STEPS OF: (A) TREATING SAID TOPPED CRUDE OIL IN A FIRST PROPANE DEASPHALTING ZONE WITH ABOUT 3 TO 10 VOLUMES OF PROPANE PER VOLUME OF CRUDE OIL AT A TEMPERATURE IN THE RANGE OF ABOUT 100 TO 180* F.; (B) RECOVERING AN OVERHEAD STREAM FRO THE FIRST ZONE OF STEP (A) COMPRISING PROPANE AND GAS OIL; (C) RECOVERING A BOTTOMS STREAM FROM THE FIRST ZONE OF STEP (A) COMPRISING ASPHALT AND PROPANE; (D) ADJUSTING THE PROPANE-ASPHALT RATIO OF THE BOTTOMS STREAM OF STEP (C) TO THE RANGE OF 1:1 TO 4:1 AND PASSING THE RESURLTING STREAM TO A SECOND PROPANE DEASPHALTING ZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF ABOUT 150 TO 200* F. AND AT LEAST 20* F. 